Many existing and emerging network services require that a served device maintain a consistently available network connection. For instance, Instant Messaging (IM) services such as Yahoo! Messenger, Jabber™, AOL® Instant MessagingSM (AIM®), and Microsoft Network (MSN®) Messenger allow a user to maintain a list of “buddies” that she can send messages to, and receive messages from, through an IM server. The user connects to the IM server by logging on through a network connection. The IM server allows the user to advertise her “presence” on the network to all or some buddies, determine the presence status of the buddies on a buddy list, and exchange messages quickly with those buddies.
Traditionally, an IM users establishes her presence from a computer with an Internet Protocol (IP) address, running IM software. The IM server notes the IP address of the computer from which presence was established, and sends IM messages directed to that subscriber to the noted IP address. This allows a subscriber to access one IM account either from, e.g., her network-connected work computer, home computer, portable computer, or PDA (Personal Digital Assistant).
Some IM services also now allow users to establish a presence at a cellular telephone that supports SMS (Short Message Service, see ETSI TS 100 901, Version 7.5.0 Release 1998, Digital cellular telecommunications system (Phase 2+), Technical realization of the Short Message Service (SMS) Point-to-Point (PP)) or WAP (Wireless Access Protocol). The cellular telephone service provider coordinates the service with the IM service provider, and provides a packet link between its network and the IM service provider. When a cellular subscriber desires to advertise an IM presence, she uses IM menu commands on the cellular telephone to contact the IM service provider, using her cellular telephone number, instead of an IP address, as a location identifier. The IM server treats a login through the cellular telephone much like a standard login from an IP address, except some IM features are handled differently and/or may not be active. The cellular telephone network provider receives IM messages or presence updates for the telephone number, translates those messages or updates into, e.g., one or more SMS messages to the appropriate cellular telephone number, and sends the SMS message(s) to the subscriber's cellular telephone.